The author supports the theory that the greenhouse effect explains the increase in earth’s temperature.

The author doesn’t suggest that scientific models are important because they predict that the earth’s temperature will continue to rise. Rather, the author’s point is that the greenhouse effect is the best explanation for the increase in earth’s temperature observed over the past 100 years. The main point concerns what explains past temperature increase; it’s not about the future.

Although the author does acknowledge that early models charting the greenhouse effect predicted greater increases in temperature than that actually observed, the author explains that after the effects of sulfates were taken into account, the observed temperature increase is consistent with models of the greenhouse effect (see P2). The author then uses this consistency as part of the support for the greenhouse effect explanation. (C) doesn’t capture the author’s support for the greenhouse effect explanation.

This best captures the main point, which is that the greenhouse effect explains the increase in the earth’s temperature. The author defends this theory from criticism in P2 and undermines an alternate theory in P3.

The author doesn’t condition the reasonableness of the greenhouse theory on the solar-fluctuation theory. In fact, the author undermines the solar-fluctuation theory as an explanation for the increased temperature in P3.